Light-sensitive sensor unit, especially for automatic switching of illumination equipment

ABSTRACT

Light-sensitive sensor unit, especially for the automatic switching of illuminating equipment, preferably in motor vehicles, which includes at least two light-sensitive sensors, at least a first sensor and a second sensor detecting the light conditions in predetermined directions. For this purpose, all light-conducting elements allocated to the sensors are to be connected in one piece as a light-conducting member and integrated into the light-conducting member of a rain sensor.

FIELD OF THE INVENTION

The present invention relates to a light-sensitive sensor unit,especially for automatic switching of illuminating equipment invehicles.

BACKGROUND INFORMATION

A sensor unit is discussed in German Published Patent Application No.195 23 262, which includes a global sensor and a directional sensor bywhich the light conditions outside the vehicle are determined. Thesensor unit is connected to the evaluation device in which, from thesignals of the sensor unit, it is ascertained whether, with the actuallypresent light conditions in the surroundings of the vehicle, a change inthe switching state of the illuminating equipment is necessary. Thissensor unit permits automatic switching of the illuminating equipment,but because of the global and directional technology, it includesrelatively many parts, which makes for considerable costs as well ascostly adjustment.

SUMMARY OF THE INVENTION

The equipment according to an exemplary embodiment of the presentinvention may have the advantage that, by the integration of global anddirectional technology, a simple, compact, robust, easy-to-install andpractically adjustment-free sensor unit may be made available. Inaddition, the equipment may include only a minimal number of componentparts, which may make possible simple and cost-effective production withbroadened functionality. Since components which hinder vision may beheld to a minimum on windshields of motor vehicles, the small dimensionsmade possible by the integration of the global and directionaltechnology may turn out to be an additional great advantage. By theintegration of the light-conducting element of the sensor unit into thelight-conducting element of a rain sensor device, further componentparts may be saved, and the number of visually impairing components onthe windshield may be even further reduced.

Further work steps may be saved especially when the light conductingelement may be manufactured by a multi-component injection moldingprocess together with the light-conducting element of the rain sensorand the coupling medium.

Because at least three sensors may detect light from predetermineddirections, a broad region in front of the vehicle may be covered.

If one sensor is positioned in the driving direction and two furthersensors are positioned tilted at an angle α to each side of the drivingdirection, this may yield a broad detecting cone in front of thevehicle, so that tunnel entrances, which are not yet in the drivingdirection, may be detected, and the illuminating equipment may beappropriately controlled.

If the directional sensors have lens-like elements which may alsooverlap with one another, the detecting cone may be matched individuallyto the instructions of the vehicle manufacturer.

If the light conducting elements are integrally formed, furtherconstruction space may be saved, and the sensor unit may be furtherminimized.

If the sensor elements are able to distinguish between daylight andartificial light, it may be prevented that the illuminating equipment isshut off at bright illumination while driving in a tunnel.

The sensor unit according to an exemplary embodiment of the presentinvention may provide a substantial improvement of the response behaviorof the rain sensor device, which may come about through the increase inthe relationship of the sensitive surface to the contact surface, ascompared to the usual rain sensors. This may be achieved by atrapeze-shaped arrangement of transmitter and receiver. Because of theoblong, coherent area, the probability may be increased that a raindroplocated on the windshield will drift onto the sensitive area because ofthe wind generated by travel of the vehicle, which may result in animprovement of the response behavior.

By using several receivers per transmitter, the number of measuredpaths, and thus the number of sensitive areas may be increased, whichmay yield a further cost advantage.

The same effect may appear when several transmitters and only onereceiver are used. If two transmitters and one receiver are used, fourmeasured paths and thus four sensitive areas may be achieved. If thedistance between the two transmitters is about twice as large as thedistance between the two receivers, this may yield an especially uniformarrangement of the sensitive areas.

It may further prove advantageous to fasten the rain sensor device onthe windshield in such a way that the installation position of thetransmitters is on the lower parallel of the trapeze and that of thereceivers on the upper parallel. Exposure to sunlight, which maypreferably come from above and which may represent disturbing outsidelight, may thus be minimized on the receivers.

Because of the improved properties, and possibly particularly because ofthe improved ratio of sensitive area to contact surface, the contactsurface of the sensor may be reduced, whereby the outer dimensions ofthe sensor on the windshield may be reduced. In this connection it maybe particularly advantageous that, because of the trapeze-shapedarrangement of the transmitters and receivers, the outer dimensions ofthe sensor housing may nevertheless be selected to be rectangular, sothat the surface area, under optimal utilization of the contact surfaceof the light-conducting member, may be arranged in it. A rectangularcontact surface or housing additionally may have a cost-reducing effectduring manufacturing. The smaller contact surface of thelight-conducting member may represent an installation advantage, sincewith a constant contact force, the contact pressure may rise, andthereby a disturbing formation of bubbles between the coupling mediumand the windshield may be avoided. In this situation it may also bepossible to partially increase the surface pressure in a targeted way,by a gentle curvature of the surface, facing the windshield, of thelight-conducting member at the light-entering and/or light-exitingsurfaces.

It may also prove advantageous if an exemplary embodiment that in thearrangement in each case two transmitters or two receivers arepositioned on the opposing parallel sides. Since, however, four measuredpaths, i.e. four sensitive surfaces of the sensor, may be realized eachby two transmitters and two receivers, a substantial cost advantage maycome about.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section through a sensor unit according to an exemplaryembodiment of the present invention.

FIG. 2 shows a representation of an exemplary embodiment of the sensorunit integrated into a light-conducting element of a rain sensor inperspective.

FIG. 3 shows a schematic drawing of the contours of an exemplaryembodiment of the rain sensor arrangement.

FIG. 4 shows a light-conducting member of the sensor unit as in FIG. 2,according to the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a sensor unit 10 according to an exemplary embodiment ofthe present invention which may be attached to a pane 11, which may be awindshield of a motor vehicle. Sensor unit 10 may be made up of severalsensors 12, and each sensor 12 may include a sensor element 13 and alight-conducting element 14, 14 a. In this instance, however, twolight-conducting elements 14 may use one sensor element 13 in common, sothat three light-sensitive sensor elements 13 may be established withfour light-conducting elements 14 and 14 a. The light-conducting member,on which light-conducting elements 14, 14 a may be mounted, may be madeup of an at least partially light-permeable plate having cylindricalprotuberances, which may be closed off with lens-shaped curvatures.Together with the lens-shaped curvatures, these cylindricalprotuberances may each form a light-conducting element 14, 14 a. Ifparallel light along the center axis of the cylindrical protuberancespasses through the lens-shaped curvatures, this may yield a focal pointf which may characterize a focal length of the light-conducting element14, 14 a.

Sensor elements 13 may each be positioned between focal points f oflight-conducting elements 14 and the light-conducting elements 14themselves. This may yield light detection cones facing ahead in thedriving direction which may permit detection in predetermineddirections. The angular aperture of the light detection cone may be setvia the distance between focal point f of each appertaininglight-conducting element 14 and light-sensitive sensor elements 13.

An evaluation device 15 may control the switching of an illuminatingdevice 16 as a function of the signals from sensor elements 13. Sensorelements 13 may all be jointly mounted on one circuit board 17, and maybe designed so that they may distinguish between daylight and artificiallight, so as to prevent switching-off by artificial light illumination,for instance in a tunnel. This may be put into effect by appropriatechoice of the sensitivity range of sensor elements 13. It may also bepossible to select the sensitivity range in such a way that certainspectral ranges or characteristic lines, such as those of gas-dischargelamps, are recognized, thus making possible control by distant light anddimmed light in a motor vehicle.

Besides this directional sensor technology, at least onelight-conducting element 14 a may be aligned forwards, not necessarilyin the driving direction. The light-detecting cone of this at least onelight-conducting element 14 a may have a very large angular aperture,and may detect the global light conditions outside the vehicle.

All light-conducting elements 14, 14 a, in particular also the sensorsof the directional technology and the global technology, may beconnected as one piece to light-conducting member 18. Thislight-conducting member 18 may be made, for example, as an extruded partof clear or UV-permeable plastic. It may also be possible to fabricatelight-conducting member 18 of dyed or coated plastic, which may have asa property a possibly desired filter action for influencing thesensitivity range of the sensor. This light-conducting member may bepressed onto the pane via a coupling medium 19, such as a silicone pad.Coupling medium 19 may prevent air occlusion between pane 11 andlight-conducting member 18, which may cause undesired scattering. It maybe further possible to mount coupling medium 19 directly on lightconducting member 18 during its production, in a multi-componentinjection molding process.

This light-conducting member 18 may be an integral component of alight-conducting member 110 of a rain sensor set-up.

FIG. 2 shows a light-conducting member 110 of a rain sensor set-up,shown in section, having a sensor housing 111. The contact surface oflight-conducting member 110 may be given, for example, by its contactvia coupling medium 19, such as a silicone pad, with pane 11. All inall, the outer dimensions of light-conducting member 110 may correspondapproximately to the length and width dimensions of the sensor unit, butsensor housing 111 may also bulbously surmount the contacted contactsurface of light-conducting member 110 on pane 11, and thereinaccommodate various elements of the sensor unit, especially transmitter114 and receiver 115, as well as a circuit board 124.

The sensor unit may, for instance, be fastened to the inside of pane 11,such as the windshield of a motor vehicle. The fastening of sensorhousing 111 to pane 11 is not shown. Light-conducting member 110 orsensor housing 111 may be fastened to pane 11 by pressing,light-conducting member 110 may characteristically have the function ofcoupling into pane 11 transmitter light 117 transmitted by a transmitter114, and of coupling out transmitter light 120, deflected by totalreflection or reflection, at another predetermined location to areceiver 115. This may happen here at optical elements 116, which may befastened, and which may be attached to the light-conducting member aslenses, and which may bundle, bend or deflect the rays of transmitterlight 117, 120 in the desired direction.

In the sectional plane shown, above light-conducting member 110 at leastone light-emitting transmitter 114 and a light-detecting receiver 115may be fastened inside sensor housing 111. Light-emitting diodes (LED)may be used as transmitters, and light-detecting diodes (LRD) may beused as receivers. The transmitter radiation of the light may lie in theinfrared (IR) or in the visual range (VIS), but other frequency rangesare also possible. A receiver element similar to a light diode in itsdesign may also be used as a receiver, whereby an optimal frequencymatching between transmitter 114 and receiver 115 may be achieved. Thematerial of light-conducting member 110 may be a plastic, and may betransparent to the transmitting frequency of the light-emitting diodes(LED), and may be opaque to interfering extraneous light.

In FIG. 3 a possible positioning of transmitter 114 and receiver 115 maybe seen. Transmitters 114 and receivers 115 of the sensor unit may beplaced near optical elements 116 of FIG. 2. Transmitter 114, receiver115 and respectively appertaining optical elements 116 may define a basearea 118 indicated by a dotted line, which may correspond to atrapezium.

On a first parallel of the trapezium, two optical elements 116 arepositioned each near a transmitter 114. Because the optical elements 116are here designed in each case as two lenses arranged next to eachother, there may follow for each transmitter 114 two measured paths intwo directions. Receivers 115 may be positioned analogously. Opticalelements 116 are made, for instance, of lenses or mirrors which may alsobe integrally formed. A solution using in each case only one lens may bepossible, since by an appropriate choice of distances a and b oftrapezoidal base area 118 the error angles created may be kept low.

Distances a and b between transmitters 114 and receivers 115 may bedetermined by the wavelength of the emitting radiation of transmitter114, the thickness of pane 11 and light-conducting member 110, the indexof refraction of pane 11, the angle of incidence and the position ofincidence of transmitter light 117 into pane 11. The distances may bepicked so that the radiation of transmitter light 117 coupled into pane11 is totally reflected one time for each measured path at the outlyingsurface of pane 11, and may subsequently be coupled out of pane 11 andguided to receiver 115.

The sketched sensitive surface 119 may correspond to the areas on thewettable side of pane 11 at which the total reflection of the radiationof transmitter light 117 may take place when pane 11 is not wetted.Depending on the arrangement of transmitters 114 and receiver 115 withrespect to pane 11, the thickness of pane 11 and the shape of opticalelement 116, the reflection surfaces of transmitter light 117 may have acertain diameter. However, the parameters named should be so large,according to the present invention, that an almost coherent sensitivesurface 119 may be created. According to the present invention, this maybe achieved by having the intersection of the center axes of radiationcone 120 of transmitter 114 lie on a straight line with the wettableside of pane 11 at about the same distance.

In case more than one total reflection is desired at the wettable outerside of pane 11, the distance a or b, of transmitters 114 and receivers115 or optical elements 116 appertaining to them in each case, may bechosen correspondingly larger, and coupling medium 19 may be attachedonly at the coupling in and coupling out areas of the light at pane 11.

FIG. 4 shows light-conducting member 110 of the sensor unit as in FIG.2, according to the present invention. Since the trapezium made up oftransmitters 114 and receivers 115 may include a shorter and a longerparallel, light-conducting member 18 of sensor unit 10 may be positionedfor automatic light control of the motor vehicle, and may be displaced alittle away from the center in the direction of the longer parallel.This light-conducting member 18 may be produced from a light-permeablematerial, whose transparency range may lie in the visual range.

Light-conducting member 110 and light-conducting member 18 may beproduced in one part, for instance in a multi-component injectionmolding process, but a design using several individual parts may also bepossible, in that case light-conducting member 18 may be set into acorresponding recess in light-conducting member 110.

Plexiglass (PMMA) may be used as the material for light-conductingmember 110, since it may be cost-effective and easy to process. Since,however, transparency may be required only in the range of thetransmitter light, another plastic may also be conceivable. Alight-conducting member material may also be suitable which may have,for example by the use of a chemical or physical method, softer and moreelastic properties on the side facing pane 11 than on the side facingaway from pane 11, since in that way coupling medium 19 may be saved.

To achieve the filtering properties of light-conducting member 110,certain substances, in particular soot particles, may be added to thematerial during the production process of light-conducting member 110,in a spatially selective manner. Thus, for example, only the regionsrequired for functioning may be permeable to transmitter light 117. Ananalogous procedure may also be possible for coupling medium 19.

In further variants, a transmitter 114 and a receiver 115 may be placedat each corner point of the trapezium or only one transmitter 114 may beused for the whole trapezium. Optical elements 116 may then havereflecting properties so as to be able, in spite of that, to couple intransmitter light 117 into pane 11 at several corner points of thetrapezium.

It may also make sense to provide special heating for integratedlight-conducting member 18, 110, in order to heat the measured pathand/or light-conducting member 18, 110. This heating item may, forinstance, be positioned on the light-conducting member as a heatingelement, or it may be realized by heating filaments, heating wires, orthe like, integrated into light-conducting member 18 and/or 110. Thismay not be a problem if light-conducting member 18, 110 is formedhomogeneously. However, if various plastics are used, for example, in amulti-component injection molding process, the expansion coefficients ofthe various plastics may be appropriately selected to avoid stresses oreven cracks in light-conducting member 18, 110. For this, one may alsoresort to other measures, such as an advantageous positioning of theheating elements or heating wires.

What is claimed is:
 1. A light-sensitive sensor unit, comprising: atleast two light-sensitive sensors, each of the at least twolight-sensitive sensors assigned a plurality of light-conductingelements, the plurality of light-conducting elements having a pluralityof predeterminable receiving characteristics, at least a firstlight-sensitive sensor and a second light-sensitive sensor detecting alight condition in at least two predetermined directions; wherein theplurality of light-conducting elements assigned to the at least twolight-sensitive sensors are connected as one piece to form alight-conducting member, the light-conducting member being integratedinto a further light-conducting member of a rain sensor unit.
 2. Thesensor unit as recited in claim 1, wherein at least threelight-sensitive sensors detect light from the at least two predetermineddirections.
 3. The sensor unit as recited in claim 1, wherein at leastone light-sensitive sensor is aligned in a predetermined drivingdirection of a vehicle.
 4. The sensor unit as recited in claim 1,wherein at least one light-sensitive sensor detects a light condition ina predetermined angle α direction, the predetermined angle α directiondefining an angle α with a straight line in a driving direction of avehicle.
 5. The sensor unit as recited in claim 4, wherein twolight-sensitive sensors define the angle α with each side of thestraight line in the driving direction of the vehicle, each of the twolight-sensitive sensors including a common light-sensitive sensorelement.
 6. The sensor unit as recited in claim 1, wherein thelight-conducting elements are integrally formed.
 7. The sensor unit asrecited in claim 1, wherein light detecting cones of thelight-conducting elements overlap.
 8. The sensor unit as recited inclaim 1, further comprising an evaluating device, the evaluating deviceable to distinguish between daylight and artificial light.
 9. The sensorunit as recited in claim 1, wherein the light-conducting member isproduced by a multi-component injection molding process.
 10. The sensorunit as recited in claim 9, wherein a plurality of components of themulti-component injection molding process are adjusted with respect to aplurality of heat expansion coefficients of the plurality of components.11. The sensor unit as recited in claim 1, wherein the rain sensor unitincludes: at least one transmitter; at least one receiver; and at leastone light-conducting member between a pane and one of the at least onetransmitter and the at least one receiver; wherein at least one image ofthe at least one transmitter and the at least one receiver forms byprojection onto the pane at least one corner point of a trapezium. 12.The sensor unit as recited in claim 11, further comprising at least onesensor element, the at least one sensor element able to distinguishbetween daylight and artificial light.
 13. The sensor unit as recited inclaim 11, wherein between the at least one transmitter and the at leastone receiver, radiation is reflected at least once at a surface of thepane, the at least one transmitter emitting radiation in variousdirections, and at least one reflection surface created therebyestablishing an at least approximately coherent sensitive surface. 14.The sensor unit as recited in claim 11, wherein the at least onetransmitter emits radiation in two directions to two of the at least onereceiver.
 15. The sensor unit as recited in claim 11, wherein the atleast one receiver receives radiation from two directions from two ofthe at least one transmitter.
 16. The sensor unit as recited in claim11, wherein: the at least one transmitter includes two transmitters; andthe at least one receiver includes two receivers.
 17. The sensor unit asrecited in claim 16, wherein the trapezium includes a symmetricaltrapezium, and wherein one of: a first distance between the tworeceivers is about double a second distance between the twotransmitters; and the second distance is about double the firstdistance.
 18. The sensor unit as recited in claim 17, wherein: the twotransmitters are positioned on a first, lower parallel in aninstallation position of the trapezium; and the two receivers arepositioned on a second, upper parallel in the installation position ofthe trapezium.
 19. The sensor unit as recited in claim 11, wherein therain sensor unit includes four measuring paths.
 20. The sensor unit asrecited in claim 11, wherein at least two centers of at least tworeflection surfaces of at least two radiation cones of at least two ofthe at least one transmitter are positioned next to one another on thepane and spaced apart at an at least approximately equal distance. 21.The sensor unit as recited in claim 20, wherein the at least two centersare positioned on a line that lies between two parallels of thetrapezium.
 22. The sensor unit as recited in claim 11, wherein the atleast one light-conducting member, the at least one transmitter, and theat least one receiver are designed and positioned so that only onesingle total reflection of a transmitter light appears on the pane. 23.The sensor unit as recited in claim 11, wherein allocated to eachtransmitter and receiver on the at least one light-conducting member isan optical element, the optical element including a plurality ofseparate lenses.
 24. The sensor unit as recited in claim 23, wherein theplurality of separate lenses are integrally formed.
 25. The sensor unitas recited in claim 23, wherein the plurality of separate lenses is twoseparate lenses.
 26. The sensor unit as recited in claim 11, wherein: anoptical element having a single lens is allocated to each of the atleast one transmitter on the at least one light-conducting member, andan optical element having a single lens is allocated each of the atleast one receiver on the at least one light-conducting member.
 27. Thesensor unit as recited in claim 1, wherein the first light-sensitivesensor detects a global ambient light.
 28. The sensor unit as recited inclaim 1, wherein the sensor unit includes a heating device for heatingthe light-conducting member.
 29. The sensor unit as recited in claim 28,wherein the heating device includes a heating element which is one of:in contact with the light-conducting member; and integrated into thelight-conducting member.
 30. The sensor unit as recited in claim 1,wherein the sensor unit is for an automatic switching of illuminatingequipment.
 31. The sensor unit as recited in claim 30, wherein thesensor unit is for a motor vehicle.
 32. The sensor unit as recited inclaim 1, wherein the light-conducting member is integrated in one piece.33. The sensor unit as recited in claim 32, wherein the light-conductingmember is produced together with the further light-conducting member ofthe rain sensor unit and a coupling medium.